In daily life, we know that carbon monoxide (CO) is a poisonous gas, but actually, CO in small doses has an important role in the body. Basically, the human body can produce small doses of CO naturally with the help of enzymes known as heme oxygenases (HO). This production of carbon monoxide occurs in various body tissues, especially in the liver, spleen and bone marrow. At small doses, CO functions as a neurotransmitter (to convey messages between nerve cells), dilates blood vessels, and serves as a cell protector. So, in small doses CO, has enormous benefits in the body.

Benefits of small doses of CO in the body

In the human brain, carbon monoxide acts as a neurotransmitter. This means that carbon monoxide can act as a neuromodulator, which is a substance that works with neurotransmitters to enhance receptor responses and can influence brain signals. Some studies have also shown that CO is an important signaling molecule in the brain. Under normal circumstances, CO can be generated in the brain from heme metabolism by Heme oxygenase-2 (HO-2). Heme is a molecule containing iron (Fe) and plays an important role in various biological processes, especially in the transportation of oxygen in the body. Heme is part of hemoglobin, a protein in red blood cells that binds and carries oxygen from the lungs to the rest of the body. CO in the brain, can modulate the release of neurotransmitters such as oxytocin and corticotropin-releasing hormone (adrenocorticotropic hormone).

Another function of CO in the body is its important role in the process of vasodilation (the condition when blood vessels dilate). This means that CO can promote relaxation of blood vessels, help with blood pressure regulation and improve blood flow. One of the first reported biological functions of CO was its ability to dilate blood vessels in several organs. The main source of CO in blood vessels is HO-2, which is expressed in muscle cells and blood vessels. CO also has an important role in Cell Protection. CO is able to reduce oxidative stress and protect cells from damage caused by inflammation or injury. Oxidative stress is a condition of imbalance in the body between free radicals (reactive molecules containing oxygen) and antioxidants (compounds that protect cells from damage). If the amount of free radicals is too high and not neutralized by antioxidants, it can cause damage to cells and tissues. Although CO is commonly known as a poisonous gas, in small doses produced naturally from the body, it has a good side that many people rarely know about

References

• Hanafy, K. A., Oh, J., & Otterbein, L. E. (2013). Carbon monoxide and the brain: Time to rethink the dogma. Current Pharmaceutical Design, 19(15), 2771–2775. https://doi.org/10.2174/1381612811319150013
• Katsnelson, A. (2019). The good side of carbon monoxide. ACS Central Science, 5(10), 1632–1635. https://doi.org/10.1021/acscentsci.9b01015
• Ryter, S. W., & Choi, A. M. K. (2013). Carbon monoxide: present and future indications for a medical gas. The Korean Journal of Internal Medicine, 28(2), 123. https://doi.org/10.3904/kjim.2013.28.2.123
• Stec, D. E., Drummond, H. A., & Vera, T. (2008). Role of carbon monoxide in blood pressure regulation. Hypertension, 51(3), 597–604. https://doi.org/10.1161/hypertensionaha.107.097154